Charging cables for charging electric vehicles are typically made safe by residual current devices (the abbreviation RCD is usually also used) which are integrated in the charging cable. Sometimes, the use of RCDs which are tripped both in the case of alternating current and in the case of direct current is required in this case. RCDs of this kind are called “type B RCDs” or “universal current-sensitive residual current devices”.
By way of example, RCDs with a rated residual current of 6 mA are used in charging cables. Particularly in the case of type B RCDs, it is necessary to ensure the requisite sensitivity and stability of the switching properties. This is because electronic components always have tolerances and temperature coefficients. In addition, a certain degree of aging, which causes deviations in the values of the RCDs, arises during the soldering process onto the printed circuit board and also when loaded during operation. Specifically charging cables which have an RCD function are subject to these influences to a greater extent than normal RCDs, which are installed in electrical distributors, owing to the use conditions. In particular, the fluctuations in respect of temperature and current loading are even greater in the case of charging cables, and this can have a strong influence on the inaccuracy of measurements which are relevant for tripping the RCD.